System and method for local number portability for telecommunication networks

ABSTRACT

One-Number-Service (ONS) allows a subscriber to keep a single Directory Number when relocating to a different access point among one or more interconnected telecommunication systems. According to one aspect of the invention, a signaling packet for a call setup to a ported number is intercepted at an improved signal transfer point where a query to a database returns a new address of the exchange the number has ported to. The new address is used to update the signaling packet at the improved signal transfer point in order to set up the call to the ported exchange. According to another aspect of the invention, an improved exchange triggers to do a query to obtain the new address of the exchange the number has ported to. The new address is used to update the signaling packet at the exchange in order to set up the call to the ported exchange. Yet other aspects of the invention include combination of query and signaling packet processing at the signal transfer point and the exchange.

FIELD OF INVENTION

The present invention relates generally to Directory Number portabilityin telecommunication systems, and more particularly to allowing asubscriber to keep a single Directory Number when relocating to adifferent access point among one or more interconnectedtelecommunication systems.

ACRONYMS

It is customary for the telecommunication industry to use acronyms whenreferring to established components and services. The ones that are usedin this disclosure are listed as follow:

AIN Advanced Intelligent Network AT Access Tandem CdPN Called PartyNumber CLEC Competitive Local Exchange Carrier DN Directory Number FCIForward CaII Indicator GAP Generic Address Parameter GTT Global TitleTranslations HLR Home Location Register IAM Initial Address Message ILECIncumbent Local Exchange Carrier IN Intelligent Network IP IntelligentPeripheral ISDN Integrated Services Digital Network ISUP ISDN UserProtocol LATA Local Access Transport Area LEC Local Exchange CarrierLIDB Line Identification Database LNP Local Number Portability (ServiceProvider's) LRN Location Routing Number LSMS Local Service ManagementSystem LTT Line Translation Table MSC Mobile Switching Center MTPMessage Transfer Part NPA Numbering Plan Area NRA Network RoutingAddress (see LRN) NXX Office Code ONS One Number Service - the numberportable service provided by the present invention OS Operations SystemsPODP 3/6/10 Digit Public Office Dialing Plan Trigger POTS Plain OldTelephone Service PX Programmable switch (also known as IntelligentPeripheral) RT Routing Table SCCP Signaling Connection Control Part SCPService Control Point SDS Specific Digit String Trigger (PODP is theterm used for this document) SMS Service Management System 557 SignalingSystem 7 SSP Service Switching Point STP Signal Transfer Point TCAPTransaction Capabilities Applications Protocol VLR Visitor LocationRegister

BACKGROUND OF THE INVENTION

A Directory Number (DN) in traditional telephone systems is used to ringa telephone on a given line of a given local telephone exchange. A localexchange may be one of many interconnecting exchanges that constitutewhat is known as the Public Switched Telephone Network (PSTN). Eachexchange, also referred to as a switch in PSTN, is provisioned with aplurality of access points or telephone lines, each addressable by a4-digit extension [YYYY]. Subscribers may call each other on the PSTN bydialing each others Directory Number. In North America the DN is a 10digit number and until recently it also represents the address of theexchange provisioning the DN. Each exchange is identified by a 6-digitexchange code [NPA-NXX] and the DN has been formed by concatenating theexchange code with the exchange extension in the format[NPA-NXX]-[YYYY].

The Directory Number (DN) then has been serving a dual function, namelyas an address for an exchange and its extension, and also as asubscriber ID (identity) number by which the subscriber could bereached. It works well if the subscriber is fixed at the originallyassigned access point or line. The problem arises when the subscribermoves to another access point. If the new access point is still servedby the same exchange, the subscriber is usually allowed to keep the samenumber since the exchange could be reconfigured to provision the sameextension number at the new access point. However, when the new accesspoint is served by a different exchange, the subscriber can no longerretain the existing DN since the new exchange will have an exchange codedifferent from that encoded in the original DN. The subscriber will haveto be given a new DN appropriate for the new exchange. In either case,every time a subscriber makes a move, it may be days or weeks before thenew service is in place.

Even if the subscriber has not moved outside the service area of anexisting exchange, the subscriber may wish to switch to a morecompetitive service provider or to subscribe to other types oftelecommunication services such as wireless, or internet or cabletelephony.

From the foregoing description, it can be seen that there are threegeneral types of number portability arising from moving from one accesspoint to another. The first is Service Provider Portability which allowsa subscriber to change access/service provider without changing the DN.The second is Location Portability which allows a subscriber to changephysical locations without changing the Directory Number. The third isService Portability which allows a subscriber to change service (e.g.,POTS to ISDN) without changing the DN. In all cases, whenever thesubscriber moves to a different exchange, the existing DN is no longercompatible with the address of the new exchange.

The lack of number portability is inconvenient for today's subscriberswho tend to be more mobile and use a variety of telecommunicationservices. Furthermore, this impedes deregulation in thetelecommunication industry, as it gives the incumbent service providerunfair advantage over a competing service provider. This is because asubscriber may be reluctant to change service provider if it also meansa change of Directory Number.

Call forwarding is one prior art solution to location numberportability. Call forwarding basically engages two directory numbers ontwo lines and redirects a first Directory Number to a second DirectoryNumber. Depending on the capability of the switched network, there aretwo ways of implementing call forwarding. One is to encode the secondDirectory Number directly into the exchange switch. The other, when theswitch is part of an IN/AIN switched network, is to trigger the switchon the DN to lookup second Directory Number from a network database.

FIG. 1A illustrates a conventional call forwarding scheme by encodingthe call forwarding information into the exchange switch. A subscriberhas a Directory Number DN1 on a telephone line L1 provisioned on anexchange X1. The subscriber is able to forward calls for DN1 to DN2,where DN2 is on a telephone line L2 provisioned on an exchange 2. Theexchange X1 is programmed to respond to call-forwarding requests by thesubscriber. In step (0), the subscriber can dial a specialcall-forwarding setup code on L1 and input into X1 the forwarding numberDN2. The exchange X1 encodes this information in its Routing Table (RT)so that if a call to DN1 is received, it is rerouted to DN2 on X2accordingly.

FIG. 1A shows a network of exchanges X0, X1 and X2 interconnected byvoice trunks. Typically, when a call connection is to be made, a callstream is established serially from one exchange to another forming aseries of circuits until the destination exchange is reached. Given theDN, each exchange has a RT that indicates which is the next exchange inthe stream to establish the link. In order to setup the linkage (callsetup) efficiently, the status and control signals associated with acall are carried in a digital network using a Signaling System 7 (SS7)protocol on it own network. The signaling is in the form of a digitalpacket know as Initial Address Message (IAM). The IAM packet is routedbetween exchanges or other points of the digital network by a SignalTransfer Point (STP) which is essentially a digital packet router. Inthe example shown, a call to DN1 originates from a line L0 of theexchange X0. The exchange X0 determines from its RT that DN1 resides inan exchange X1 and proceeds to set up the call. The call setup involves,in step (1), forming an IAM0(DN1) packet to be routed from X0 to X1 bythe STP, and with which the a circuit between X0 and X1 is madeavailable. At X1, its RT indicates that DN1 is forwarded to DN2 at X2.Then in step (2) an IAM1(DN2) packet reflecting the redirection isrouted form X1 to the exchange X2 that is provisioning DN2 to set up thenext leg of the circuit. In this way, a call made to DN1 is forwarded toconnect at DN2.

The switch-based call-forwarding scheme has several disadvantages. TwoDirectory Numbers, DN1 and DN2, are engaged and therefore the solutionis uneconomical. Furthermore, this two-number solution is not symmetricin that when dialing out from the forwarded-to line L2, the line isstill identified with DN2. To set up the call-forwarding service, thesubscriber must initiate it from the original access point L1. Also, thecall routing is not efficient, as all calls for DN1 must first visit theoriginal exchange X1 before being rerouted to X2.

FIG. 1B illustrates another conventional call forwarding scheme asimplemented by an Intelligent Network or Advanced Intelligent Network(IN/AIN). In this type of intelligent network, the interconnectingswitches X1, X2, . . . cooperate with one or more programmable switch(PX) also known as Intelligent Peripheral (IP) and a database serverknown as Service Control Point (SCP).

In step (0), to activate the call-forwarding feature, a subscribertypically dials an 800 number which connects the subscriber to an IP.After authentication, the subscriber can input the original DN1 and thenew DN2 number. The IP interacts with SCP to have the forwarding of DN1to DN2 entered into the SCP. It then interacts with the switch X1 tohave the call-termination trigger set on the switch to trigger on thecall-forwarded number DN1. Subsequently, when a call to DN1 is receivedin X1, it will trigger X1 to obtain the call-forwarding informationdirecting to DN2 by performing a lookup on the SCP. The switch X1 thenuses the retrieved information to route the call to X2, L2.

In the example shown in FIG. 1B, a call to DN1 originates from a line L0of the exchange X0. The exchange X0 determines from its Line TranslationTable (LTT) that DN1 resides in an exchange X1 and proceeds to set upthe call. The call set up involves, in step (1), forming an IAM0(DN1)packet to be routed by the STP to X1, by which the a voice circuitbetween X0 and X1 is made available. In step (2), at X1, the call to DN1triggers a query through the STP to lookup forwarding information fromthe SCP. In step (3) the SCP returns the call forwarding informationabout DN2. In step (4) X1 uses the DN2 information to form its IAM1(DN2)packet. Then in step (5) the IAM1(DN2) packet is routed form X1 to theexchange X2 that is provisioning DN2 to set up the next leg of the voicecircuit. In this way, a call made to DN1 is forwarded to connect at DN2.

The intelligent network-based call-forwarding scheme improves on theswitch-based scheme in that the call-forwarding information is nothard-coded into the exchange but rather retrievable from a more flexibledatabase. The service need not be set up at the original access point L1but could be set up by the subscriber from any access point including L2that has access to the IP. Otherwise, it still has the samedisadvantages as that of switch-based scheme.

Another prior art solution to number portability is directed to ServiceProvider Portability which is a result of recent government mandates inthe United States of America. There has been legislation to deregulatethe telecommunication industry, primarily to transform a monopolisticindustry controlled by a handful of tightly regulated incumbenttelephone companies to a plurality of competing telecommunicationcompanies operating in a free market setting. To this end, anyconditions that accord unfair advantages to the incumbent companies mustbe dismantled. As mentioned before, user inertia owing to the lack ofnumber portability among service providers is one such concern. Thisconcern has been addressed in the United States Communications Act of1996. The 1996 Act defines (Service Provider) “number portability” as“the ability of users of telecommunications services to retain, at thesame location, existing telecommunications numbers without impairment ofquality, reliability or convenience when switching from onetelecommunications carrier to another.” Overseeing compliance of the1996 Act, the United States Federal Communications Commission (FCC) hasordered telephone companies to implement Service Provider Portabilityaccording to the Local Routing Number (LRN) method. The LRN method isspecified in a series of publications, the latest of which is “GenericSwitching and Signaling Requirements, Issue 1.05, Aug. 1, 1997, editor:J. J. Lichter, Lucent Technologies.

The essence of LRN method is to decouple the subscriber's ID functionfrom the exchange address function of the Directory Number (DN). The DNwill be considered primarily as an ID number for a given subscriber. Theexchange that has ported numbers will have an address independently anduniquely given by the Local Routing Number (LRN) which is a 10-digitnumber. If the DN is not ported from its originating exchange, then theexchange's LRN can still be obtained from the DN. On the other hand, ifthe DN is ported to a second exchange, then the second exchange must beaddressed by its own LRN which is different from that obtained from theDN.

FIG. 2A illustrates the LRN scheme for implementing Service ProviderPortability as required by the United States Local Number Portability(LNP) authorities. The LNP scheme is designed for DN portability fromone service provider to another servicing the same locality or LocalAccess Transport Area (LATA). Initially, it will offer DN portabilitybetween an Incumbent Local Exchange Carrier (ILEC), shown as ServiceProvider N, and a Competitive Local Exchange Carrier (CLEC), shown asService Provider 2. Basically, it employs the dynamic lookup capabilityof an IN/AIN switched network In addition to the SCP database, eachservice provider is provisioned with an additional LNP-SCP database forstoring the routing information for a ported subscriber. In particular,the routing information will contain the LRN of an exchange that a givenDN has ported to. When a call to a DN that has been predefined as LNPportable, the Service Control Point's (SCP) service logic programmed inthe exchange will initiate an AIN or IN based LNP query to the LNP-SCPto obtain the LRN for the destination exchange to which the DN that hasbeen ported. The queried LRN is then returned to the exchange to routethe call accordingly.

In the example shown, a subscriber was given DN1 when originallysubscribed to a line L1 provisioned by an exchange X1 of ServiceProvider N. When the subscriber subsequently changes to Service Provider2, DN1 has been ported to a line L2 on an exchange X2. In step (0) thechange in service provider is submitted by both Service Provider N andService Provider 2 to an inter-service provider mediation service whooversees the incorporation of the porting information into the LNP-SCPdatabases of the various service providers. Thus, over a period of daysor weeks, the porting information, DN1 together with the address of X2(i.e. LRN(X2))) are entered into the respective LNP-SCP of ServiceProvider N, Service Provider 2 and Service Provider N−1 as shown in FIG.2.

In addition to mediation and storing of LRNs in the LNP-SCP database ofthe various service providers, the LNP implementation also mandates theexchanges to be “LNP-enabled”, i.e. upgraded to be able to handle theLRN scheme.

At some point, a connecting exchange must look up the ported informationfrom one of the LNP-SCPs in order to complete the circuit to the portedlocation. Part of the LNP scheme is to minimize the burden imposed onthe service provider being ported from (Service Provider N) for doingthe lookup, but to let the service provider adjacent to it (ServiceProvider N−1) to perform the lookup and routing. Thus, when a call ismade to DN1, it is typically routed to Service Provider N−1 beforeattempting to do a lookup.

In the example shown in FIG. 2, a call to DN1 is made from a line L0 inone of the exchanges X0 of Service Provider N−1. In step (1), theLNP-enabled exchange triggers on DN1 to do a query for LRN. In step (2),this induces a STP to lookup LRN(DN1) from LNP-SCP. In step (3), theaddress of the destination exchange, X2=LRN(DN1), is returned to X0. Instep (4), a call setup is initiated from X0 to an Access Tandem exchange(AT). The LAM0(DN1, LRN(DN1)) being routed from X0 to AT now has the LRNof X2. In step (5), the AT set ups the next leg of the connection andconnects into the domain of the Service Provider 2 containing thedestination exchange X2. In steps (6) and (7), through call setups, theconnection is made all the way to the destination exchange X2 where thecall is connected to a designated line L2.

Since only one LNP-SCP lookup need be made to obtain the portinginformation, the exchanges are designed to sense whether a lookup hasbeen made or not. This is accomplished in the LRN method by setting aflag in the IAM signaling packet that is passed from exchange toexchange. The LRN method specifies that the nth bit of the Forward CallIndicator (FCI) field of the IAM is to be used for this purpose (SeeFIG. 5(a)). If an LNP-SCP lookup has not been made, the exchangeresponsive to that condition will initiate a lookup, otherwise no lookupwill be made.

FIG. 5(c) shows the IAM field values after a LNP query. This applies tothe case in which a DN1 originated from an exchange X1 is ported to anexchange X2 with an address LRN2 using the LRN method. In the LRNmethod, the address of the destination exchange is obtained from theCDPN field. Thus, it is the field in which the Local Routing Number(LRN) is entered. After an LNP query, the address of the destinationexchange LRN2 is returned and placed in the CDPN field. Under the LRNmethod, the GAP field is used to store the directory number DN1. Also,after an LNP query has been performed, the nth bit of the FCI field isset to “1”to prevent subsequent exchanges from repeating the query.

U.S. Pat. No. 5,758,281 issued May 26, 1998 to Emery et al. discloses asystem for allowing a user to send and receive calls from a singleportable handset using a single assigned number whether at home orroaming.

The following publications discloses Advance Intelligent Network (AN)and their exchanges, SS7, STP and the LNP scheme, relevant portions ofthem are incorporated herein by reference.

“The Intelligent Network Standards: their application of services”,Faynberg, I., et al, McGraw-Fill, 1997

“Mobile and Wireless Networks”, Black, Uyless. Prentice Hall, 1996.

“BellCore specification of SS7”, GR-246-CORE, Decmber. 1995, BellCore.

“Common Channel Signaling Network Interface Specification”, GR-905-CORE,March 1995, BellCore.

“ITU-TS specifications of signaling system Number 7”, CCITT “white Book”Volume VI, Fasciles VI.7, VI.9 (Q.700 Series Recommendations).

“AIN 0.1 Switching Requirements”, TR-NWT-001284, BellCore

“AIN 0.2 Switch-Intelligent Peripheral Interface Generic Requirements”,GR-1129-CORE, BellCore

“AIN Switch-Service Control point/ Adjunct Interface GenericRequirements”, GR-1299-CORE, Decmber. 1995, BellCore

“LNP capability specifications”, GR-2936-CORE Draft, May 1996, BellCore.

“STP generic Requirements”, GR-82-CORE, December. 1995, BellCore.

“Compatibility Information for Interconnection of a wireless serviceprovider and a local exchange carrier network” GR-145, May 1998,BellCore

“Telephone Number Portability; NANC Recommendation concerning LNPadministration, wireless and wireline integration”, CC docket No.95-116, NSD file No. L-98-84

The LRN method has been designed to narrowly address number portabilitybetween service providers serving the same locality. While the LRNmethod introduces the important feature of LRN addressing of theexchanges, independent of the Directory Number, there remains nouniversal single-number portability solution. For example, given theservice provider LNP implementation, a subscriber may retain the DN whenswitching service provider within the same LATA, but still has problemswhen moved to another exchange. Similarly, the problem of having asingle DN between wire-line and wireless, or between other communicationsystems such as internet or cable telephony, is still not addressed.

It would be desirable for the subscriber to be able to retain his or herDirectory Number when accessing from different access points of aplurality of interconnected communication systems.

OBJECTS AND SUMMARY OF THE INVENTION

Accordingly, it is a general object of the present invention to providea system and method for number portability from one access point toanother among one or more interconnected telecommunication systems.

It is an object of the present invention to provide a system and methodfor One-Number-Service (ONS) which enables a subscriber's directorynumber to be easily ported from one access point to another among one ormore interconnected telecommunication systems.

It is an object of the present invention to provide a system and methodfor One-Number-Service (ONS) which enables a subscriber's directorynumber to be easily ported from one access point to another among aLocal Access Transport Area (LATA).

It is an object of the present invention to provide a system and methodfor One-Number-Service (ONS) which enables a subscriber's directorynumber to be easily ported from one service provider to another serviceprovider.

It is an object of the present invention to provide a system and methodfor One-Number-Service (ONS) which enables a subscriber's directorynumber to be easily ported between different telecommunication services.

It is an object of the present invention to provide a cost effective andreliable system and method for number portability from one access pointto another among one or more interconnected telecommunication systems.

These and additional objects are accomplished by providing a system andmethod for maintaining and accessing number portability information inorder to complete a call to a ported directory number to its portedlocation. In particular these objects are accomplished by enhancingexisting telecommunication systems in a cost effective manner, withminimum modification.

According to one aspect of the invention, in an intelligent (IN/AIN)telecommunication network system, the Signal Transfer Points (STPs) areenhanced into One-Number-Service STPs or (OSTPs) to query the address ofthe exchange the directory number has ported to during a call setupprocess and to modify the call setup accordingly. In particular, thedirectory number contained in the signaling packet for a call setup isexamined and used to look up a database containing the new address (LRN)of the exchange the directory number has ported to. The address fieldfor the destination exchange in the signaling packet is then updatedwith the new address in order for the call setup to complete the call tothe ported exchange.

In one embodiment, all ported numbers, whether they are LNP-portednumbers (i.e., between service providers by the LRN method) orONS-ported numbers (i.e., between two access points in general) areprocessed by OSTP query during call setup.

In another embodiment, where the telecommunication network systemsupports Service Provider portability or MNP), directory numbers thatare LNP-ported are handled by the LNP scheme which requires anLNP-enabled exchange to perform a query by means of a TransactionCapable Application Part (TCAP) signaling via a STP to a databasecontaining the new address (LRN) of the exchange the directory numberhas ported to. One-Number-Service (ONS) portability is accomplished byusing the LNP scheme to handle the LNP-ported numbers and the OSTP queryduring call setup for other non LNP-ported directory numbers or for LNPdirectory numbers that have been ported more than once.

The conventional LRN method is very expensive as it involves costlymodification to all the exchanges. In any case, it still does notaddress other number portability outside that of service providers′. TheONS scheme provided by OSTP query during call setup is advantageousbecause unlike the LRN method the plurality of interconnecting exchangesneed not be modified, instead, only the relatively fewer STPs need beenhanced to become OSTPs.

According to another aspect of the invention, where thetelecommunication network system supports Service Provider portabilityor (LNP), directory numbers that are LNP-ported are handled by the LNPscheme which requires an LNP-enabled exchange to perform a query bymeans of a TCAP signaling via a STP to a database containing the newaddress (LRN) of the exchange the directory number has ported to. WhenOne-Number-Service (ONS) portability is applied within a serviceprovider's domain, it is accomplished by an enhanced STP with TCAPprocessing that responsive to an ONS-ported number, queries a databasecontaining ONS porting information.

According to yet another aspect of the invention, the exchanges amongthe telecommunication network system are enhanced to query a databasecontaining LNP porting information in response to an LNP-porteddirectory number, and to query a database containing ONS portinginformation in response to an ONS-ported directory number.

Additional objects, features and advantages of the present inventionwill be understood from the following description of the preferredembodiments, which description should be taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates a conventional call forwarding scheme by encodingthe call forwarding information into the exchange switch;

FIG. 1B illustrates another conventional call forwarding scheme asimplemented by an Intelligent Network or Advanced Intelligent Network(IN/AIN);

FIG. 2 illustrates the LRN scheme for implementing Service ProviderPortability as required by the U.S. Local Number Portability MNP)authorities;

FIG. 3 is a schematic illustration of a typical operating environment ofthe present invention for implementing One-Number-Service (ONS) in whicha directory number may be retained when moving from one access point toanother among interconnected telecommunication systems;

FIG. 4 is a flow diagram illustrating the actions and signaling of anexchange and an Enhanced Signal Transfer Point (OSTP) when implementingOne-Number-Service (ONS) according to a general embodiment of thepresent invention;

FIGS. 5(a)-5(e) list a number of fields in the ISUP Initial AddressMessage (IAM) that have bearing on number portability;

FIG. 6 is a functional block diagram of an enhanced Signal TransferPoint (OSTP) according to a preferred embodiment of the presentinvention;

FIG. 7 is a flow diagram of the call setup processing of the OSTP packetswitch of FIG. 6 for implementing One-Number-Service (ONS) portabilityaccording to a preferred embodiment of the present invention;

FIG. 8 is a flow chart for implementing One-Number-Service (ONS),according to another aspect of the present invention; and

FIG. 9 is a flow diagram illustrating the actions and signaling of anExchange and a Signal Transfer Point (SIP) when implementingSingle-Number-Service (ONS) according to another aspect of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 3 is a schematic illustration of a typical operating environment ofthe present invention for implementing One-Number-Service (ONS) in whicha directory number (DN1) may be retained when moving from one accesspoint to another among interconnected telecommunication systems.

A public switched telephone network (PSTN) is constituted from aplurality of local domains such as domains 10, 12, individually operatedby different service providers such as Service Provider 2 and ServiceProvider N. Each local domain provides telephone service through accesslines such as L2 and L3 provisioned in one or more exchanges 20 such asX2 and X3. The exchanges are interconnected by a voice trunk network 30and are connectable to other portions of the PSTN via an access tandem(AT) 22.

Signaling between the exchanges 20 is carried by a SS7 (Signal System 7)network 40. One or more Signal Transfer Point (STP) is provided to routethe SS7 signals between points in the SS7 network. Each exchange has aSS7 network interface known as its Service Switching Point (SSP) (notshown). Each exchange represents a point in the SS7 network and isaddressable by a point code. In a local domain, typically there are fromtens to over one hundred exchanges serviced by a pair of STPs.

According to one aspect of the invention, at least one STP enhanced withthe features of the invention and denoted by OSTP 50 is provided at eachlocal domain. The OSTP is preferably located as a gateway STP such thatit can receive and process signaling first entering the domain.

In an Intelligent or Advanced Intelligent Network (IN/AIN), a set ofdatabases 60 as provided by one or more Service Control Point (SCP) suchas 62, 64 may be installed as a point in the SS7 network. The SCP 60 isa database for providing service related information or number portinginformation and is available for an exchange to retrieve informationdynamically via an STP. As described earlier, in a network where serviceprovider portability has been implemented, a LNP-SCP 62 has been addedto store service provider number porting information. In one preferredembodiment of the present invention, a database OSCP 70 for storinginformation about ported number across arbitrary access points is alsoprovided. The OSCP 70 is connectable to the OSTP 50 via the SS7 network40 and/or via a high-speed connection 72. The set of databases 60 ismaintained by a Local Service Management System (LSMS) 80.

The One-Number-Service (ONS) of the present invention provides numberportability across arbitrary access points among a plurality ofinterconnected telecommunication systems and therefore encompassesdirectory number portability across different locations, differentservices, as well as different service providers.

One or more wireless telephone domain 100 is connectable to the PSTN viaconnection to the voice trunk network 30 and the SS7 signaling network40. Each wireless domain 100 provides wireless telephone service throughaccess channels provisioned in one or more mobile switching center (MSC)102. Each access channel is assignable to a subscriber's mobile handsetsuch as h3. The MSCs serve as the counterpart to the exchange and STP ofthe PSTN and are connected to the voice trunk 30 and the SS7 network 40.The wireless telephone domain 100 typically operates with a number ofdatabases to keep track of the subscribers. A Visitor Location Register(VLR) is used to keep track of subscribers active among the cells servedby the MSC. Similarly, a Home Location Register (HLR) is used to keeptrack of the home location of a subscriber. In the preferred embodiment,a STP enhanced with the features of the invention and denoted by OST 50′is provided in each wireless domain 100. Also, a database OSCP 70′ forstoring information about ONS ported numbers is provided for operationwith the OSTh 50′.

One or more internet telephony domain 110 is connectable to the PSTN viaconnection to the voice trunk network 30 and the SS7 signaling network40. Each Internet telephony domain 110 provides internet telephoneservice through a programmable switch (PX) 112 where a plurality ofaccess lines are provisioned therein. The PX 112 serves as thecounterpart to the exchange of the PSTN and are connected to the voicetrunk 30 and the SS7 network 40. An internet gateway 114 serves toconnect the provisioned access lines to access points on an internetnetwork 116 such as a handset h3 installed on a workstation. In thepreferred embodiment, a STP enhanced with the features of the inventionand denoted by OSTP 50″ is provided in each internet telephony domain110. Also, a database OSCP 70″ for storing information about ONS portednumbers is provided for operation with the OSTP 50″. Reference toIP-telephony may be found, for example, in ITU-T, Visual TelephoneSystems and Equipment for Local Area Networks, Which Provide aNon-Guaranteed Quality of Service, Rec. H.323, November. 1996, Geneva,Switzerland, the disclosure of which is herein incorporated byreference.

One or more cable telephony domain 120 is connectable to the PSTN viaconnection to the voice trunk network 30 and the SS7 signaling network40. Each cable telephony domain 120 provides internet telephone servicethrough a programmable switch (PX) 122 where a plurality of access linesare provisioned therein. The PX 122 serves as the counterpart to theexchange of the PSTN and are connected to the voice trunk 30 and the SS7network 40. A cable gateway 124 serves to connect provisioned accesslines access points on a cable network 126 such as a handset h3installed on a cable modem on the cable network. In the preferredembodiment, a STP enhanced with the features of the invention anddenoted by OSTP 50′″ is provided in each cable telephony domain 110.Also, a database OSCP 70′″ for storing information about ONS portednumbers is provided for operation with the OSTP 50′″.

FIG. 4 is a flow diagram illustrating the actions and signaling of anexchange X 20 and an Enhanced Signal Transfer Point (OSTP) 50 whenimplementing One-Number-Service (ONS) according to a general embodimentof the present invention.

Step 202: A call to the directory number DN1 is routed to the presentExchange X.

Step 204: A digit analysis is performed on DN1

Step 206: DN1 is checked against a line translation table (LLT) to seeif the number is provisioned in Exchange X. Control proceeds to Step 208if it is, otherwise control proceeds to Step 220.

Step 208: Since DN1 is provisioned in Exchange X, connection is made toaccess line to complete the call.

Step 210: Call connection is completed.

Step 220: Since DN1 is not provisioned in Exchange x attempt is made todetermine which exchange it resides on. First, it is determined ifExchange X is LNP-enabled. If it is, LNP lookup of the LRN (address) ofthe designation exchange is possible and control proceeds to Step 222.Otherwise, it is just a standard exchange and a standard call setup isdone in Step 230.

Step 222: Since Exchange X is LNP-enabled, next, DN1 is checked todetermined if it is native to a LNP-enabled exchange. If it is, controlproceeds to Step 224 for the next step in LNP lookup. Otherwise, DN1 isnative to a non-LNP-enabled exchange and a standard call setup is donein Step 230.

Step 224: Since DN1 has been determined to be in the LNP scheme, alookup to determine the LRN of the exchange it has ported to ispossible. In this case, DN1 was originally provisioned on Line L1 ofExchange X1 of Service Provider 1 (not shown). It has since been portedto L2 of X2 of Service Provider 2. The LNPQueryFlag in the IAM messageis checked to see if an LNP lookup has already been made. If the flag isnot set, control proceeds to do an LNP lookup in Step 226. Otherwise,LNP lookup has already been done and control proceeds to Step 240.

Step 226: A TCAP signal is issued to the OSTP 50 to perform a LNPlookup. The STP or OSTP uses the SCCP (Signaling Connection Control Partof the exchange) to process and route the TCAP (Transaction CapabilitiesApplications Protocol) message to the SCP or OSCP. The OSTP 50 processesthe TCAP request with TCAP processing component 54 whereupon thedatabase 60 is looked up using DN1 to retrieve the associated LRN2. Theaddress of the destination exchange is then returned by the OSTP 50 tothe Exchange X 20, and control proceeds to Step 228.

Step 228: The LNPQueryFlag in the IAM is set to prevent further LNPlookups. Control then proceeds to Step 240.

Step 230: The IAM is one of a standard IAM and is sent as an ISUP signalto the OSTP 50.

Step 240: The IAM already contains the LRN2 of the destination addressobtained from a previous LNP lookup, and is sent as an ISUP signal tothe OSTP 50 to be processed by the ISUP processing component 52.

Step 250: After processing by the ISUP processing component 52, the IAMpacket is routed from the OSTP 50 to the next point in the SS7 network.

FIGS. 5(a)-5(e) list a number of fields in the ISUP Initial AddressMessage (IAM) that have bearing on number portability. FIG. 5(a) showsthe names of three fields of interest, namely, Called Party Number(CdPN), Generic Address Parameter (GAP) and Forward Call Indicator(FCI).

FIG. 5(b) illustrates the IAM field values during a call setup of anon-ported DN or one whose ported address has not been queried. The CdPNfield basically carries information about the address of the destinationexchange. In this case, the address of the destination exchange issimply given by the NPA-XXX portion of the DN, and therefore DN isentered in the CdPN field.

FIG. 5(c) shows the IAM field values after a LNP query. This applies tothe case in which a DN1 originated from an exchange X1 is ported to anexchange X2 with an address LRN2 using the LRN method. In the LRNmethod, the address of the destination exchange is obtained from theCdPN field. Thus, it is the field in which the Local Routing Number(LRN) is entered. After an LNP query, the address of the destinationexchange LRN2 is returned and placed in the CdPN field. Under the LRNmethod, the GAP field is used to store the directory number DN1. Also,after an LNP query has been performed, the “nth” bit of the FCI field isset to “1” to prevent subsequent exchanges from repeating the query.

FIG. 6 is a functional block diagram of an enhanced Signal TransferPoint (OSTP) according to a preferred embodiment of the presentinvention. As mentioned earlier, the network of voice trunks areswitched by a plurality of interconnecting exchanges to establish avoice trunk circuit for a call. At the same time, the signalingassociated with the call process is transported by a Signal System 7(SS7) network in which one or more Signal Transfer Points (STPs)performs the switching to transfer the signaling packet from one pointto another point among the SS7 network. With each exchange having a SS7interface, namely a Service Switching Point (SSP), it is a transferpoint in the SS7 network from which the STP transfers the signaling fromone exchange to another exchange. Typically, an exchange issues a SS7signaling packet to a STP, and the STP assigns the address of the nexttransfer point (point code) in the SS7 network and switches thesignaling packet on its way towards the next transfer point which may beanother exchange, STP or some other destination in the SS7 network.

In FIG. 6, the OSTP 50 is a STP enhanced with the features of thepresent invention. A SS7 I/O interface controller 262 receives a SS7packet from an input 260 and allows it to interact with aprocessor-based intelligent system before sending it out as an outputSS7 packet via an output 264. An internal bus 270 couples theprocessor-based intelligent system to the SS7 I/O interface controller262. The processor-based intelligent system further comprises aprocessor 272 that operates in conjunction with a number of memories. Aread-only-memory (ROM) 274 is used to store firmware for the processor.A random-access-memory (RAM) 276 provides the memory space for theprocessor 272 to operate in. A mass-storage 280 provides non-volatileand easily updateably storage of programs and other informationincluding possibly routing and number porting information. A GlobalTitle Translation table (GTT) 282 is preferably maintained in themass-storage 280. The GTT is basically a routing table for looking up apoint code (address in the SS7 network) with a given directory number.

In one embodiment, number porting information in the form of an ONS-SCPdatabase is also stored in the mass storage 280 within the OSTP 50. Inanother embodiment, the ONS-SCP database resides in an external databaseserver (see FIG. 3) and communicates with the OSP 50 via a high-speedlink 72 to an ONS Database Server interface 290 coupled to the internalbus 270.

The SS7 protocol has two main stacks in a multi-layer structure: an ISDNUser Part (ISUP); and a Transaction Capability Application Part (TCAP).ISUP signaling is used to communicate call setup information. Asmentioned in an earlier section, the call setup information is embodiedin an Initial Address Message IAM. Signaling that is of a query natureis communicated using the TCAP. TCAP signalings are becoming more commonwith the advent of intelligent networks, as there are increasingapplications in which the call process includes a query to a database(SCP) on the network.

FIG. 7 is a flow diagram of the call setup processing of the OSTP packetswitch of FIG. 6 for implementing One-Number-Service (ONS) portabilityaccording to a preferred embodiment of the present invention. Asdescribed in an earlier section, a call circuit transverses the networkfrom an originating exchange to the destination exchange. The circuit isestablished exchange-by-exchange with the aid of call setup signaling inthe form of the IAM being transferred from exchange to exchange by meansof the OSTP. In particular, the GAP field and the CdPN field in the IAMenables the next exchange to be determined along the formative circuit.

In step 310, an input SS7 message is analyzed to determine if it is anISUP (call setup) message or a TCAP (query) message. If it is an ISUPmessage, it is processed through an ISUP block 52′. If it is a TCAPmessage, it is processed through a TCAP block 54′.

In the present embodiment, the TCAP block 54′ basically processes thesame way as a conventional STP in executing a LNP query. The STP usesSCCP layer for GTT. This means that a TCAP query is directed to a SCPdatabase, and the returned result is in turn returned by the STP in step350 to the querying exchange.

The ISUP block 52′ basically receives the call setup message as anInitial Address Message (IAM) and processes it in the following steps:

Step 322: the directory number DN1 is parsed out from the input IAMmessage.

Step 324: Whether DN1 is ported or not would have previously beenentered into the Global Title Translation (GTT) table in the OSTP. Theentry for the directory number DN1 is looked up to obtain the point code(address of the next point in the SS7 network.)

Step 326: The entry for DN1 in the GTT is coded such that if DN1 is notONS (One-Number-Service of the present invention) ported, there is noentry found in the GTT and the default point code would be the same asthat of a conventional STP in processing a call setup, and the IAM wouldbe sent out of the OSTP in Step 350 to the next point in the SS7network.

Step 340: The entry for DN1 in the GTT is coded such that if DN1 is ONS(One-Number-Service of the present invention) ported, there would be anentry found in the GTT and the looked up point code would point to anONS-SCP database.

Step 342: The ONS-SCP is looked up by the OSTP using DN1.

Step 344: The address of the exchange LRN3 to which DN1 has ported to isreturned.

Step 346: The OSTP modifies the IAM by updating the CdPN field with LRN3(see FIG. 5(e)), and the control proceeds to step 350.

Step 350: The IAM message, either unmodified from step 326 or modifiedfrom step 346, is output from the OSTh to the next point in the SS7network which is the next leg of the call setup process.

One feature of the present aspect of the invention is to implementdatabase lookup of ONS ported numbers by means of an enhanced STP,instead of the LNP method of enhancing the exchange to initiate thelookup via the TCAP component of a STP. The IAM in an ISUP message ismodified on-the-fly with the looked up LRN.

FIG. 5(d) illustrates the state of the IAM after OSTP initiated ONSlookup. Again, the address of the destination exchange LRN3 is returnedfrom the ONS-SCP and placed in the CdPN field of the IAM.

In contrast, in conventional STP routing of the IAM packet, the exchangeissuing the IAM already determines where the packet should go. Therouting is done at the lower, Message Transfer Part (MTP) layer, and theSTP routes the packet directly to the next point in the SS7 network.

FIG. 8 is a flow chart for implementing One-Number-Service (ONS),according to another aspect of the present invention. The infrastructureset up to perform LNP portability is employed to implement the ONSportability of the present invention. As described in an earliersection, LNP portability is implemented by an LNP ported number firstbeing recognized at a LNP-capable exchange. This will trigger a query toan LNP database (LNP-SCP). The query is done via a STP in which the ISUPpart is conventional, but the TCAP part of the SS7 message enableslookup to either an ONS or LNP database and the STP returns a queryresult to the exchange.

In the present embodiment, a TCAP block 54″ is improved over that of aconventional STP in executing a LNP type query. In particular, the LNPtype query is further determined whether it is an whether it is an ONSquery in which case an ONS database should be looked up, or an actualLNP query in which case an LNP database should be looked up. In eithercases, the queried result is returned by the STP to the queryingexchange.

In step 310, an input SS7 message from an exchange is analyzed todetermine if it is an ISUP (call setup) message or a TCAP (query)message. If it is an ISUP message, it is processed conventionally andproceeded to be routed to the next point in the SS7 network via theoutput step 350. If it is a TCAP message, it is processed through theTCAP block 54″ of the invention.

If the SS7 message is an ISUP message, the exchange issuing the ISUPmessage has already determined where the message packet should go. Therouting is done at the lower, Message Transfer Part (MTP) layer, and theSTP simply routes the packet to the next point in the SS7 network.

The TCAP block 54″ includes the following steps:

Step 431: the directory number DN1 is parsed out from the input messageand checked to see if it is an ONS ported number. If it is an ONS portednumber, control proceeds

to Step 432. Otherwise control proceeds to Step 442 for LNP processing.

Step 432: The directory number DN1 is identified to be a ported numbersupported in the ONS system, and control proceeds to Step 434.

Step 434: The entry for the directory number DN1 is looked up to obtainthe point code (address of the next point in the SS7 network.). The DN1would have previously been entered into the Global Title Translation(GTT) table in the OSTP. If DN1 is ONS ported, its entry will have apoint code pointing to an ONS database, and control proceeds to Step436.

Step 436: ADN1 entry is found in the GTT and the looked up point codewould point to an ONS-SCP database. The control then proceeds to Step437.

Step 437: The ONS-SCP is looked up by the OSTP using DN1.

Step 438: The address of the exchange LRN3 to which DN1 has ported to isreturned. The control proceeds to Step 450.

Step 442: The directory number DN1 is identified to be a ported numbersupported in the LNP system, and control proceeds to Step 444.

Step 444: The entry for the directory number DN1 is looked up to obtainthe point code (address of the next point in the SS7 network.). The DN1would have previously been entered into the Global Title Translation(GTT) table in the OSTP. If DN1 is LNP ported, its entry will have apoint code pointing to an LNP database, and control proceeds to Step446.

Step 446: A DN1 entry is found in the GTT and the looked up point codewould point to a LNP-SCP database. The control then proceeds to Step446.

Step 447: The LNP-SCP is looked up by the OSTP using DN1.

Step 448: The address of the exchange LRN2 to which DN1 has ported to isreturned. The control proceeds to Step 450.

Step 350: The returned LRN is output from the OSTP and returned to theexchange that initiated the query.

FIG. 9 is a flow diagram illustrating the actions and signalings of anExchange X 20 and a Signal Transfer Point (STP) 50 when implementingOne-Number-Service (ONS) according to another aspect of the presentinvention.

Step 502: A call to the directory number DN1 is routed to the presentExchange X.

Step 504: A digit analysis is performed on DN1

Step 506: DN1 is checked against a line translation table (LTT) to seeif the number is provisioned in Exchange X Control proceeds to Step 508if it is, otherwise control proceeds to Step 520.

Step 508: Since DN1 is provisioned in Exchange X, connection is made toaccess line to complete the call.

Step 510: Call connection is completed.

Step 512: Since DN1 is not provisioned in Exchange X, attempt is made todetermine which exchange it resides on. First, it is determined ifExchange X is ONS-enabled. If it is, ONS lookup of the LRN (address) ofthe designation exchange may be possible and control proceeds to Step514. Otherwise, control proceeds to Step 520 to test if Exchange X isLNP-enabled.

Step 514: Since Exchange X is ONS-enabled, next, DN1 is checked todetermined if it is native to an ONS-enabled exchange. If it is, controlproceeds to Step 516 for the next step in ONS lookup. Otherwise, DN1 isnative to a non-ONS-enabled exchange and control proceeds to Step 520.

Step 516: A TCAP signal is issued to the STP 50 to perform an ONSlookup. The database 80 (see FIG. 4) is looked up using DN1 to retrievethe associated LRN2. The address of the destination exchange is thenreturned by the STP 50 to the Exchange X 20, and control proceeds toStep 518.

Step 518: The LNPQueryFlag in the IAM is set to prevent further LNPlookups. Control then proceeds to Step 540.

Step 519: The IAM packet is routed by the STP 50 to the next point inthe SS7 network and towards the exchange having LRN3.

Step 520: First, it is determined if Exchange X is LNP-enabled. If itis, LNP lookup of the LRN (address) of the designation exchange may bepossible and control proceeds to Step 522. Otherwise, control proceedsto Step 530.

Step 522: Since Exchange X is LNP-enabled, next, DN1 is checked todetermined if it is native to a LNPenabled exchange. If it is, controlproceeds to Step 524 for the next step in LNP lookup. Otherwise, DN1 isnative to a non-LNP-enabled exchange and a standard call setup is donein Step 530.

Step 524: Since DN1 has been determined to be in the LNP scheme, alookup to determine the LRN of the exchange it has ported to ispossible. The LNPQueryFlag in the IAM message is checked to see if anLNP lookup has already been made. If the flag is not set, controlproceeds to do an LNP lookup in Step 526. Otherwise, LNP lookup hasalready been done and control proceeds to Step 540.

Step 526: A TCAP signal is issued to the OSTP 50 to perform a LNPlookup. The database 80 (see FIG., 4) is looked up using DN1 to retrievethe associated LRN2. The address of the destination exchange is thenreturned by the STP 50 to the Exchange X 20, and control proceeds toStep 528.

Step 528: The LNPQueryFlag in the IAM is set to prevent further LNPlookups. Control then proceeds to Step 540.

Step 530: The IAM is one of a standard IAM and is sent as an ISUP signalto the STP 50.

Step 539: The IAM packet is routed by the STP 50 to the next point inthe SS7 network and towards the exchange having LRN1.

Step 540: The IAM already contains the LRN of the destination addressobtained from a previous LNP lookup, and is sent as an ISUP signal tothe STP 50 to be processed by the ISUP processing component 52.

Step 549: The IAM packet is routed by the OSTP 50 to the next point inthe SS7 network and towards the exchange having LRN2.

Step 550: After processing by the ISUP processing component 52, the IAMpacket is routed from the STP 50 to the next point in the SS7 network.

FIG. 5(e) illustrates the state of the IAM after an ONS query has beenperformed. The address of the destination exchange LRN3 is returned andentered into the CdPN field.

While the embodiments of the various aspects of the present inventionthat have been described are the preferred implementation, those skilledin the art will understand that variation thereof may also be possible.Therefore, the invention is entitled to protection within the full scopeof the appended claims.

It is claimed:
 1. In a telecommunication system having a group ofinterlinked, addressable exchanges, where a call is routed to adestination exchange therein, the call routing being setup incooperation with a signaling packet containing an address of thedestination exchange passed between exchanges routing the call, a methodof porting a subscriber's directory number from a first access pointprovisioned in a first exchange to a second acces point provisioned in asecond exchange among said group of exchanges, comprising: providing adatabase for obtaining an address of an exchange provisioning a givendirectory number, said database being accessible by said group ofinterlinked, addressable exchanges; maintaining said database to reflectsaid subscriber's directory number being provisioned by the secondexchange instead of the first exchange; and intercepting a signalingpacket associated with a call to said subscriber's directory number,wherein said intercepting results in additional steps, including:querying said database with said subscriber's directory number to obtainan address for the second exchange; and modifying the address of thedestination exchange contained in the intercepted signaling packet bysubstituting it with that of the second exchange; and passing themodified signaling packet to an exchange among said group of exchangesso that said call to said subscriber's directory number is routed to thesecond exchange accordingly.
 2. A method of porting a subscriber'sdirectory number as in claim 1, wherein: the first exchange includes oneselected from a wireline, wireless, cable network, local-area network orwide-area network telecommunication system.
 3. A method of porting asubscriber's directory number as in claim 1, wherein: the secondexchange includes one selected from a wireline, wireless, cable network,local-area network or wide-area network telecommunication system.
 4. Amethod of porting a subscriber's directory number as in claim 1, whereinthe first and second exchange are one and the same.
 5. A method ofporting a subscriber's directory number as in claim 1-4, wherein saiddatabase is one of a plurality of databases accessible to said group ofinterlinked, addressable exchanges.
 6. A method of porting asubscriber's directory number as in claim 1-4, further comprising:providing a signal transfer processor for performing the steps ofintercepting a signaling packet, querying said database, and modifyingthe address of the designation contained in the intercepted signalingpacket.
 7. A method of porting a subscriber's directory number as inclaim 1-4, wherein: said step of querying said database furtherincluding determining if said subscriber's number is a ported numberbefore performing the querying of said database.
 8. A method of portinga subscriber's directory number as in claim 1-4, wherein the steps ofintercepting a signaling packet, querying said database, and modifyingthe address of the designation contained in the intercepted signalingpacket are performed under an established Integrated Service DigitalNetwork User Part protocol of a predefined signaling system network. 9.In a telecommunication system having a group of interlinked, addressableexchanges serviced by a service provider, where a call is routed to adestination exchange therein, the call routing being set up incooperation with a signaling packet containing an address of thedestination exchange passed between exchanges routing the call, a methodof porting a subscriber's directory number from a first access pointprovisioned in a first exchange to a second access point provisioned ina second exchange among said service provider, comprising: providing adatabase for said group of interlinked, addressable exchanges to obtainan address of an exchange provisioning a given directory number;maintaining said database to reflect said subscriber's directory numberbeing provisioned by the second exchange instead of the first exchange;causing one of said interlinked addressable exchanges, in response tosaid subscriber's directory number, to query said database with saidsubscriber's directory number to obtain an address for the secondexchange, said query including determining if said subscriber's numberis a ported number before performing the querying of said database;using the address for the second exchange to construct the signalingpacket for the call routing being set up; and passing the signalingpacket to another exchange among said group of exchanges so that saidcall to said subscriber's directory number is routed to the secondexchange accordingly.
 10. A method of porting a subscriber's directorynumber as in claim 9, wherein: the first exchange includes one selectedfrom a wireline, wireless, cable network, local-area network orwide-area network telecommunication system.
 11. A method of porting asubscriber's directory number as in claim 9, wherein: the secondexchange includes one selected from a wireline, wireless, cable network,local-area network or wide-area network telecommunication system.
 12. Amethod of porting a subscriber's directory number as in claim 9, whereinthe first and second exchange are one and the same.
 13. A method ofporting a subscriber's directory number as in claim 9-12, wherein saiddatabase is one of a plurality of databases accessible to said group ofinterlinked, addressable exchanges.
 14. A method of porting asubscriber's directory number as in claim 9-12, further comprising:providing a signal transfer processor for performing the steps ofquerying said database in response to said subscriber's directory numberto obtain an address for the second exchange.
 15. A method of porting asubscriber's directory number as in claim 14, wherein said signaltransfer processor performing the step of querying under an establishedTransaction Capable Application Part protocol of a predefined signalingsystem network.
 16. In a telecommunication system having a group ofinterlinked, addressable exchanges, where a call is routed to adestination exchange therein, the call routing being setup incooperation with a signaling packet containing an address of thedestination exchange passed between exchanges routing the call, animproved exchange, comprising: a first trigger responsive to one of afirst set of directory numbers to cause a first query of a firstdatabase containing porting information of said one of a first set ofdirectory numbers, said first query returning an address for the secondexchange; a second trigger responsive to another one of a second set ofdirectory numbers to cause a second query of a second databasecontaining porting information of said another one of a second set ofdirectory numbers, said second query returning an address for the secondexchange; means for constructing the signaling packet for the callrouting being set up using the address for the second exchange; andmeans for passing the signaling packet to another exchange among saidgroup of exchanges so that said call to said subscriber's directorynumber is routed to the second exchange accordingly.
 17. An improvedexchange as in claim 16, wherein: the first exchange includes oneselected from a wireline, wireless, cable network, local-area network orwide-area network telecommunication system.
 18. An improved exchange asin claim 16, wherein: the second exchange includes one selected from awireline, wireless, cable network, local-area network or wide-areanetwork telecommunication system.
 19. An improved exchange as in claim16, wherein the first and second exchange are one and the same.
 20. Animproved exchange as in claim 16, wherein the first set of directorynumbers is associated with Local Number Porting (LNP).